TY - JOUR
T1 - A single atom change turns insulating saturated wires into molecular conductors
AU - Chen, Xiaoping
AU - Kretz, Bernhard
AU - Adoah, Francis
AU - Nickle, Cameron
AU - Chi, Xiao
AU - Yu, Xiaojiang
AU - del Barco, Enrique
AU - Thompson, Damien
AU - Egger, David A.
AU - Nijhuis, Christian A.
N1 - Funding Information:
We acknowledge fruitful discussions with Ayelet Vilan (Weizmann Institute of Science) and Gemma Solomon (University of Copenhagen). Fundings by the Ministry of Education (MOE) for supporting this research under award No. MOE2019-T2-1-137 and R-143-000-B30-112 are acknowledged. Prime Minister’s Office, Singapore under its Medium sized centre programme is also acknowledged for supporting this research. The authors would furthermore like to acknowledge the Singapore Synchrotron Light Source (SSLS) for providing the facilities at the Surface, Interface and Nanostructure Science (SINS) beam line under NUS core support C-380-003-003-001. The Laboratory is a National Research Infrastructure under the National Research Foundation Singapore. We moreover acknowledge funding from the Alexander von Humboldt Foundation within the framework of the Sofja Kovalevskaja Award, endowed by the German Federal Ministry of and Research, and the Technical University of Munich—Institute for Advanced Study, funded by the German Excellence Initiative and the European Union Seventh Framework Programme under Grant Agreement No. 291763. D.T. thanks Science Foundation Ireland (SFI) for support (awards Grant Numbers 15/CDA/3491 and 12/RC/2275_P2) and for computing resources at the SFI/Higher Education Authority Irish Centre for High-End Computing (ICHEC). Finally, we also acknowledge support from the U.S. National Science Foundation (Grant No. ECCS#1916874). The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for funding this project by providing computing time through the John von Neumann Institute for Computing (NIC) on the GCS Supercomputer JUWELS at Jülich Supercomputing Centre (JSC).
Publisher Copyright:
© 2021, The Author(s).
Financial transaction number:
342121738
PY - 2021/12
Y1 - 2021/12
N2 - We present an efficient strategy to modulate tunnelling in molecular junctions by changing the tunnelling decay coefficient, β, by terminal-atom substitution which avoids altering the molecular backbone. By varying X = H, F, Cl, Br, I in junctions with S(CH2)(10-18)X, current densities (J) increase >4 orders of magnitude, creating molecular conductors via reduction of β from 0.75 to 0.25 Å−1. Impedance measurements show tripled dielectric constants (εr) with X = I, reduced HOMO-LUMO gaps and tunnelling-barrier heights, and 5-times reduced contact resistance. These effects alone cannot explain the large change in β. Density-functional theory shows highly localized, X-dependent potential drops at the S(CH2)nX//electrode interface that modifies the tunnelling barrier shape. Commonly-used tunnelling models neglect localized potential drops and changes in εr. Here, we demonstrate experimentally that β∝1/εr, suggesting highly-polarizable terminal-atoms act as charge traps and highlighting the need for new charge transport models that account for dielectric effects in molecular tunnelling junctions.
AB - We present an efficient strategy to modulate tunnelling in molecular junctions by changing the tunnelling decay coefficient, β, by terminal-atom substitution which avoids altering the molecular backbone. By varying X = H, F, Cl, Br, I in junctions with S(CH2)(10-18)X, current densities (J) increase >4 orders of magnitude, creating molecular conductors via reduction of β from 0.75 to 0.25 Å−1. Impedance measurements show tripled dielectric constants (εr) with X = I, reduced HOMO-LUMO gaps and tunnelling-barrier heights, and 5-times reduced contact resistance. These effects alone cannot explain the large change in β. Density-functional theory shows highly localized, X-dependent potential drops at the S(CH2)nX//electrode interface that modifies the tunnelling barrier shape. Commonly-used tunnelling models neglect localized potential drops and changes in εr. Here, we demonstrate experimentally that β∝1/εr, suggesting highly-polarizable terminal-atoms act as charge traps and highlighting the need for new charge transport models that account for dielectric effects in molecular tunnelling junctions.
KW - UT-Gold-D
UR - http://www.scopus.com/inward/record.url?scp=85107580656&partnerID=8YFLogxK
U2 - 10.1038/s41467-021-23528-8
DO - 10.1038/s41467-021-23528-8
M3 - Article
C2 - 34103489
AN - SCOPUS:85107580656
SN - 2041-1723
VL - 12
JO - Nature communications
JF - Nature communications
IS - 1
M1 - 3432
ER -